Pheromone Gene Diversification and the Evolution of Courtship Glands in Plethodontid Salamanders.

Proteinaceous pheromones that diversify through gene duplication can result in shifts in courtship cocktails that may serve as a mechanism for reproductive isolation. The molecular evolution of pheromones has been extensively studied in salamanders, but how these genes and associated novel courtship glands have codiversified has not been evaluated. In this study we used transcriptional analyses to examine the relationship between pheromone diversification and gland type in three divergent lineages of plethodontid salamanders.

Sociality sculpts similar patterns of molecular evolution in two independently evolved lineages of eusocial bees.

While it is well known that the genome can affect social behavior, recent models posit that social lifestyles can, in turn, influence genome evolution. Here, we perform the most phylogenetically comprehensive comparative analysis of 16 bee genomes to date: incorporating two published and four new carpenter bee genomes (Apidae: Xylocopinae) for a first-ever genomic comparison with a monophyletic clade containing solitary through advanced eusocial taxa. We find that eusocial lineages have undergone more gene family expansions, feature more signatures of positive selection, and have higher counts of taxonomically restricted genes than solitary and weakly social lineages.

Genetic signatures of dominance hierarchies reveal conserved cis-regulatory and brain gene expression underlying aggression in a facultatively social bee.

Agonistic interactions among individuals can result in the formation of dominance hierarches that can reinforce individual behavior and social status. Such dominance hierarches precede the establishment of reproductive dominance, division of labor and caste formation in highly social insect taxa. As such, deciphering the molecular basis of aggression is fundamental in understanding the mechanisms of social evolution.

Multiple stressors produce differential transcriptomic patterns in a stream-dwelling salamander.

Background: Global biodiversity is decreasing at an alarming rate and amphibians are at the forefront of this crisis. Understanding the factors that negatively impact amphibian populations and effectively monitoring their health are fundamental to addressing this epidemic. Plasma glucocorticoids are often used to assess stress in amphibians and other vertebrates, but these hormones can be extremely dynamic and impractical to quantify in small organisms.

Conserved Genes Underlie Phenotypic Plasticity in an Incipiently Social Bee.

Despite a strong history of theoretical work on the mechanisms of social evolution, relatively little is known of the molecular genetic changes that accompany transitions from solitary to eusocial forms. Here, we provide the first genome of an incipiently social bee that shows both solitary and social colony organization in sympatry, the Australian carpenter bee Ceratina australensis. Through comparative analysis, we provide support for the role of conserved genes and cis-regulation of gene expression in the phenotypic plasticity observed in nest-sharing, a rudimentary form of sociality.

Heterochrony repolarized: a phylogenetic analysis of developmental timing in plethodontid salamanders.

Background: Disentangling evolutionary shifts in developmental timing (heterochony) is dependent upon accurate estimates of ancestral patterns. However, many classic assessments of heterochronic patterns predate robust phylogenetic hypotheses and methods for trait reconstruction, and therefore may have been polarized with untested 'primitive' conditions. Here we revisit the heterochronic modes of development that underlie the evolution of metamorphosis, maturation, and paedomorphosis in plethodontid salamanders.

Reduced effects of thyroid hormone on gene expression and metamorphosis in a paedomorphic plethodontid salamander.

It has been over a century since Gudernatsch (1912, Wilhelm Roux Arch Entwickl Mech Org 35:457-483) demonstrated that mammalian thyroid gland extracts can stimulate tadpole metamorphosis. Despite the tremendous developmental diversity of amphibians, mechanisms of metamorphosis have mostly been studied in a few model systems. This limits our understanding of the processes that influence the evolution of developmental aberrations.

Larval masquerade: a new species of paedomorphic salamander (Caudata: Plethodontidae: Eurycea) from the Ouachita Mountains of North America.

Species with truncated developmental patterns may go undetected if they resemble the juveniles of their close relatives. Herein we present an example of this phenomenon with the description of a highly divergent, relict species of stream-dwelling plethodontid salamander from the Ouachita Mountains of North America. Both mitochondrial and nuclear sequence data show that this new species is most closely related to its syntopic relative, Eurycea multiplicata.

Evolution of paedomorphosis in plethodontid salamanders: ecological correlates and re-evolution of metamorphosis.

Life-history modes can profoundly impact the biology of a species, and a classic example is the dichotomy between metamorphic (biphasic) and paedomorphic (permanently aquatic) life-history strategies in salamanders. However, despite centuries of research on this system, several basic questions about the evolution of paedomorphosis in salamanders have not been addressed. Here, we use a nearly comprehensive, time-calibrated phylogeny of spelerpine plethodontids to reconstruct the evolution of paedomorphosis and to test if paedomorphosis is (1) reversible; (2) associated with living in caves; (3) associated with relatively dry climatic conditions on the surface; and (4) correlated with limited range size and geographic dispersal.

Spontaneous activity of dopaminergic retinal neurons.

Dopaminergic local circuit neurons in the retina (DA cells) show robust, spontaneous, tetrodotoxin-sensitive pacemaking. To investigate the mechanism underlying this behavior, we characterized the sodium current and a subset of the potassium currents in the cells in voltage-clamp experiments. We found that there is a persistent component of the sodium current in DA cells which activates at more depolarized potentials than the transient component of the current.